In recent years, electrochemical devices, especially lithium secondary batteries have been widely used as power supplies for electronic devices such as mobile telephones, notebook-size personal computers and the like, power supplies for electric vehicles, as well as for electric power storage. These electronic devices and vehicles may be used in a broad temperature range, for example, at midsummer high temperatures or at frigid low temperatures, and are therefore required to be improved in point of the discharge capacity in a broad temperature range even after long-term use.
In this specification, the term of lithium secondary battery is used as a concept including so-called lithium ion secondary batteries.
For example, it is known that, in a lithium secondary battery using a highly-crystalline carbon material such as natural graphite, artificial graphite or the like as the negative electrode material therein, the decomposed product generated through reductive decomposition of the solvent in the nonaqueous electrolytic solution on the surface of the negative electrode during charging detracts from the electrochemical reaction favorable for the battery, therefore worsening the cycle property of the battery. Deposition of the decomposed product of the nonaqueous solvent interferes with smooth absorption and release of lithium by the negative electrode, and therefore, in particular, the load characteristics at low temperatures may be thereby often worsened.
In addition, it is known that a lithium secondary battery using a lithium metal or its alloy, or a metal elemental substance such as tin, silicon or the like or its metal oxide as the negative electrode material therein may have a high initial battery capacity but its battery performance such as battery capacity and cycle property greatly worsens, since the micronized powdering of the material is promoted during cycles thereby bringing about accelerated reductive decomposition of the nonaqueous solvent, as compared with the negative electrode of a carbon material. In addition, the micronized powdering of the negative electrode material and the deposition of the decomposed product of the nonaqueous solvent may interfere with smooth absorption and release of lithium by the negative electrode, and therefore, in particular, the load characteristics at low temperatures may be thereby often worsened.
On the other hand, it is known that, in a lithium secondary battery using, for example, LiCoO2, LiMn2O4, LiNiO2 or LiFePO4 as the positive electrode, when the nonaqueous solvent in the nonaqueous electrolytic solution is heated at a high temperature in the charged state, the decomposed product thereby locally generated through partial oxidative decomposition in the interface between the positive electrode material and the nonaqueous electrolytic solution interferes with the electrochemical reaction favorable for the battery, and therefore the cycle property and the low-temperature property after cycles are thereby also worsened.
As in the above, the decomposed product generated through decomposition of the nonaqueous electrolytic solution on the positive electrode or the negative electrode interferes with the movement of lithium ions, and the battery performance is thereby worsened. Despite the situation, electronic appliances equipped with lithium secondary batteries therein are offering more and more an increasing range of functions and are being in a stream of further increase in the power consumption. With that, the capacity of lithium secondary batteries is being much increased, and the space volume for the nonaqueous electrolytic solution in the battery is decreased by increasing the density of the electrode and by reducing the useless space volume in the battery. Accordingly, the situation is that even decomposition of only a small amount of the nonaqueous electrolytic solution may worsen the battery performance at low temperatures.
Patent Reference 1 shows that, in a lithium secondary battery in which the battery interterminal off-load voltage is at least 4.25 V at 25° C. at the end of charging, a compound having two specific sulfonyloxy groups bonding to each other via a linking group therebetween ([Chemical Formula 1] in [Claim 1]) is effective for enhancing the cycle property at 25° C. and for preventing gas generation in continuous charging at 60° C. Further, in Paragraph [0039] therein, there are mentioned 1,4-benzenediol disulfonates each having only one of two and the same substituents, sulfonyloxy groups on the benzene ring. However, even when the compound of the type is added to a nonaqueous electrolytic solution, the low-temperature property after high-temperature cycles is not still sufficiently satisfactory.
Patent Reference 2 provides a reagent capable of sufficiently functioning as an overcharge preventing mechanism even when used in a 4 V-level battery to be charged with a large current, and shows a nonaqueous electrolytic solution using for secondary battery which uses the reagent and which therefore enjoys the advantages of high energy density, excellent safety and cost reduction. The patent reference shows, as one example of the reagent of the type, 1,2-dimethoxybenzene having only two and the same substituents, alkoxy groups on one benzene ring, which, however, has a problem in that the low-temperature property after high-temperature cycles rather worsen.
Patent Reference 3 shows that, when an electrolytic solution containing a biphenyl derivative such as 4-phenylphenyl methanesulfonate or the like added thereto is used therein, then a lithium secondary battery can be provided that is excellent in cycle property in charging and discharging under a high voltage condition of such that the uppermost voltage is higher than 4.1 V and/or under a high temperature condition of not lower than 40° C., and is further excellent in battery characteristics such as electric capacity and storage property in a charged state.
Patent Reference 4 shows that use of an electrolytic solution containing 2-cyclohexylphenylmethyl carbonate added thereto improves the safety in overcharging of a lithium secondary battery and the high-temperature storage property thereof.
As a lithium primary battery, for example, used is one in which the positive electrode is formed of manganese dioxide or fluorographite and the negative electrode is formed of lithium metal, and the lithium primary battery of the type is widely used as having a high energy density, for which, however, it is desired to prevent the increase in the internal resistance after storage at high temperatures and to enhance the discharge characteristics in a broad temperature range even after storage.
Further, recently, as a new power source for electric vehicles or hybrid electric vehicles, an electric double-layer capacitor that uses active carbon or the like as the electrode thereof has become developed from the viewpoint of the output density, and from the viewpoint of satisfying both the energy density and the output density, an electric storage device of a hybrid capacitor based on the combination of the storage principle of a lithium ion secondary battery and that of an electric double-layer capacitor (the hybrid capacitor of the type takes advantage of both the lithium absorption/release capacitance and the electric double-layer capacitance), which may be referred to also as a lithium ion capacitor, has become developed; and for these, development of the discharge performance in a broad temperature range even after long-term use is desired.